At 21:07 17/05/96 -0700, you wrote:
>
>Dear Mems experts
>
>I have two visiting students from Germany who are
>making ultrathin SiN force microscope cantilevers,
>of order 350-800 Angstroms thick and up to 200
>microns long.
>
>The last stage of the process is an anisotropic
>etch in KOH to free the cantilevers from the
>underlying silicon, followed by critical point
>drying in C02.
>
>During the etch, the Si bubbles like crazy,
>to the extend that we are surprised that the
>cantilevers even survive!
>
>Survive they do, however we would like
>to suppress the bubbling if possible.  Can
>anyone offer any suggestions?  We apologize
>if this is a well-know problem with a well
>known solution.... it is only well known
>to those who know it well (which is not us!)
>
>Best wishes from a fan of MEMS ... John Sidles
>
>
>
In a paper on NH4OH/water based silicon etching (Schnakenberg et al; Sensors
and actuators A, 25-27,(1991), 1-7) H2O2 is added to the solution to improve
surface roughness. I have not tried adding this to KOH chemistry but it may
have the effect of reducing or eliminating the bubbling.

Martin Geear
Nortel Technology
London Road, Harlow
Essex, CM17 9NA, UK
Phone: +44 1279 403677
FAX: +44 1279 402765
e-mail: Martin.Geear@nortel.co.uk